Historic districts are often the witness of a city's historical development. Because the historical block concentrates various structures and historical remains in different stages of urban development, it has a direct witness role in understanding the development of human civilization and the development course of the city. Secondly, due to the different historical development of different cities, diverse urban features and architectural forms have been formed. Thirdly, historic districts are the most distinctive places of urban life and the containers for local customs and habits. Therefore, historic districts are valuable tourism resources for the tourism industry of thousands of cities.